Mercury switch



Mrch, 1946. H, L. LAMBERT MERCURY SWITCH 2 Sheets-Sheet l Filed Aug. 2l, 1943 March 5,.1946.l H. l., LAMBERT MERCURY swITcH Filed Aug21} 194:5

' KNENT'OR.. f

Patented Mar. 5, 1946 MERCURY SWITCH Harry L. Lambert, Enfield, N. Y., assignor, by mesne assignments, to Walter J. Pickering, New

York, N. Y.

Application August 21, 1943, Serial No. 499,498

(Cl. 20D-80) 11 Claims.

This invention relates to mercury tube switches, and particularly to those which make or break a circuit in response to centrifugal action.

An object of this invention is to provide an im proved mercury tube type of switch which when rotated will make and break a circuit as the speed of rotation Varies on opposite sides of a predetermined speed; which will be efiective in any posie tion; which may have the air removed and replaced with an inert atmosphere in a relatively.

simple manner; which will be exceptionally sensitive even at high speeds, and open or close the circuit within a very small change in the speed of rotation, which will not be dependent upon gravity or surface tension for its action; which will be relatively simple, compact, efficient, du` rable and inexpensive; and with which the speed at which it breaks the circuit may be varied in a. simple manner.

Other objects and advantages will be apparent from the following description of two embodiments of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

Fig. 1 is an end face elevation of a rotary member having mounted thereon a switch constructed in accordance with this invention;

Fig. 2 is a side elevation of the same with a portion broken away to show an interior construction, and showing how the switch controls the speed of a motor a-s one application of the invention;

Fig. 3 is a longitudinal sectional elevation through the switch element with the mercury in the position occupied when the switch is rotating at a very low rate;

Fig. 4 is a similar sectional elevation, but showing the position of the mercury when the circuit is opened through one of two branch circuits;

Fig. 5 is a similar sectional elevation showing the position of the mercury when the switch is horizontal and not rotating;

Fig. 6 is an end elevation vof the same;

Fig. 7 is a longitudinal, sectional elevation siniilar to Fig. 3, but illustrating a modification of the construction there shown; and

Fig. 8 is an end elevation of the same.

In the embodiment of the invention illustrated. in Figs. l to (i, my improved mercury tube, switch element I includes a generally cylindrical, glass tube or housing 2 which is removably clamped be tween a pair of spring fingers 3 that are turned up from opposite side edges of a base or plate 4, so as to form a spring clamp with oppositely bowed,

arcuate zones intermediate the ends of the clamp arms to partially nt and grip the cylindrical tube of the switch. This tube 2 has a chamber C and a pointed tip 5 formed when the shell or housing is exhausted of its air and replaced with an inert atmosphere, as usual in mercury tube switches. after, of course, a quantity of mercury 6 has been placed within the chamber 1 of the housing but which only partially fills it. The base or plate 4 has an up-turned lug E beyond the flanges 3 which has an aperture in which the tip 5 is received. This lug 6 tends to prevent centrifugal forces from moving the housing or switch element 2 endwise in the clips 3.

The plate 4 is coniined against a face of a ro tatabl-e block 1 of insulating material in any suitable manner, such as by headed studs 8, the Shanks of which extend through a slot 9, Fig. l, provided in the plate 4 and extending in a direction endwise thereof. These studs 8 confine the plate 4 against the block 1, with the plate 4 disposed approximately radially of the axis of rotation A-B of the block 1, so that the plate l4 may be moved radially of the axis to the extent permitted by engagement of the studs 8 in the ends of the slot. The block 1 is secured upon a rotatable shaft Ill having its axis coincident with the axis A-`B. The end of plate 4 nearest the axis oi rotation is provided with an outwardly turned arm or flange II through which a screw I2 is threaded. This screw I2 has a knurled head I3 on its outer end by which the screw may be turned, so as to thread it back and forth through the flange or arm II to diierent extents.

Adjacent to the head I3, the screw is provided with a reduced smooth shank which is rotatably received in a bearing I4 and held thereby against endwise movement. The bearing I4 is secured to the block 1 in any suitable manner, such as by having a projecting threaded stud screwed into the block 1, as shown in Fig. 2. By turning the head I3, the screw I2, which can rotate but not move endwise, will be threaded through the flange or arm II in one direction or the other, and this will move the switch element I toward or from the axis of ,rotationy depending upon the direction of rotation of the screw I2. Thus, by this adjustment when one moves the switch element to different distances from the axis of rotation, this positions the switch element to open its circuit at different speeds.

In the embodiment of the switch element I shown in Figs. 3 to 6, the housing 2 is provided in its interior with a cylindrical ange or projection I 5 which extends from the end of the housing 3 nearest the axis of rotation, towards and nearly to the opposite end wall of the chamber C, but terminating a short distance from it.

Within the sub-chamber I6 defined by the cylindrical wall I5, I mount a member Il which is oatable in mercury and of a material which is unaffected by the mercury. This member I1 is of such size that it moves freely along the interior of sub-chamber I8 in a direction toward and from the axis of rotation of the housing.

A spiral compression spring I 8 is disposed in the chamber I5, with one end abutting against the inner end of that chamber and the other end encircling a boss I9 on the adjacent end of the member I I. This spring I3 urges the float member I'I toward the open end of the chamber I6, or in other words, in a direction away from the axis of rotation of this housing.

A plurality of conductors 2n, 2I and 22 pass through the base end wall of the housing 2 into the chamber C and there are wound spirally about the outside periphery of the cylindrical wall I in a direction toward the opposite end of the chamber, but with the turns of the diierent conductors spaced from one another and all terminating at diierent distances from the end wall having the tip 5. One of the conductors, such as 23. extends farthest towards the cuter end wall of the housing, and the other conductors terminate at progressively shorter distances from that end of the housing.

The iloat member II is normally held by the spring I8 against the outer end of the chamber wall and in doing so, it displaces enough of the mercury which is coniined in that end zone of the housing by rotation of the housing about axis A-B, so that the mercury will engage and electrically connect all of the conductors 20, 2I and 22. As the speed of rotation increases. the centrifugal forces acting on the mercury will increase the force with which the mercury is crowded into the outer end of the chamber 1.

While the same centrifugal forces also tend to hold the float member I'I in the outer end of the housing, as shown in Fig. 3, in addition to the force exerted by the spring I8, nevertheless, since the float member I'I is lighter than the mercury, the centrifugal forces acting on tlae mercury will be greater than those acting on the member I'I, with the result that the mercury will displace or float the member I'I away from the outer end of the housing as shown in Fig. 4.

When a certain critical speed is reached, the mercury will have been caused to move outwardly and displace the float member until the mercury disengages from the conductor` 2I. Since the conductor extends well into the body of mercury, this separation of the mercury from conductor 2 I will open a circuit between the conductors 2D and 2l through the mercury. The conductor 22 extends somewhat farther into the mercury than the conductor 2I, and if the speed of rotation continues to increase, the mercury will by centrifugal action displace the float farther in a direction toward the axis of rotation, and this receding mercury will then separate from the conductor 22 at some other, higher critical speed. If the conductor 2U is a common conductor, then this separation of mercury from the conductor 22 will open a branch circuit between conducf tors 23 and 22 through said mercury.

The external circuits, in which the conductor 20 is a common wire and conductors 2| and 22 are branch wires, may be controlled by this mercury tube switch so that the branch circuits will be opened at different critical speeds. Such branch circuits may be used for any suitable purpose, such as to operate signals or other apparatus, or they may be used to control the speed of a motor that provides a rotative force for the block I.

In Fig. 2 l have illustrated the application of such circuits to the control of the speed of a motor M, and that system will now be briefly explained. Referring particularly to Fig. 2, the conductors 20, 2| and 22 are connected respectively through the block I to annular collecting rings 23, 24 and 25, which rings are arranged concentrically with one another and with the shaft I0, but on the opposite face of the block 'I from the switch element. Brushes 26, 2l and 28 are carried on some relatively stationary support and bear upon these collecting rings so as to establish connections therewith while the block 'I and switch element are rotating with the shaft I0. Suitable circuit wires are connected to these brushes and to the apparatus to be controlled, but in this illustrated arrangement, all of these wires are used to control the speed of the motor M, through connections that will now be described.

A wire 29 connects the brush 26 to one side of the motor M, the other side of the motor M being connected through a switch 30 to line wire L1. The line wire L2 is connected through the switch 30 to the brush 2I. The brush 23 is connected by a wire 3I to a contact 32 of a switch 33, the other side of the switch being connected to the wire 29. With this arrangement, to start the motor one closes the switch 30, and a circuit will be established from line wire Ll through switch 30, motor M, wire 29, brush 26, ring 24, conductor 2I, mercury 6, common conductor 20, ring 23, brush 21, and line wire L2. The motor then opcrates, and assuming that the switch 33 is open, the speed of the motor will then increase until the centrifugal forces acting on the mercury 6 will displace the oat member II enough to allow the mercury to recede from the contact 2I as shown in Fig. 4. Since the switch 33 is open, the branch circuit through the conductor 22 is open, and the separation of the mercury from conductor 2| will open the circuit through the'motor. The speed of the motor will then decrease, and as the centrifugal forces also then decrease, the spring I8 will force the float member Il further back into the mercury and cause the mercury to again engage the conductor 2|. This reestablishes the circuit through the motor, and the speed will again increase until the circuit is again opened. This will maintain the speed of the motcr at a definite, predetermined speed within close limits. This speed may be varied by turning the button I3 of the screw I2 to shift the housing of the switch element toward or from the axis ci rotation A-B.

If now one desires to have the motor operate at a higher speed, the switch 33 is closed which completes the branch circuit through the conductor 22. The motor circuit will be the same as just described above, except that separation of the mercury from conductor 2I will not open the circuit through the motor, because a branch circuit of the motor is established through the switch 33, contact 32, wire 3|, brush 28, ring 25, and conductor 22, mercury 6, conductor 20, ring 23, brush 2'I, and line wire L2. The motor will thus continue to increase its speed until the mercury also recedes from the conductor 22, which opens the circuit through the motor and prevents further increase of speed, in the same way that the separation of mercury from conductor 2| controlled the speed of the motor M.

Since the conductors are wound spirally on the exterior of the cylindrical flange I5, the mercury will engage and connect all of said conductors if the tube should be in some other position than' a vertical position, and not rotating. It is for example in a horizontal position in Fig. 5, and it will be observed there how the mercury connects all of these conductors 20, 2|, and 22. As soon as the shaft I begins to rotate, the mercury will be moved into the outer end zone by centrifugal action Where it will remain while rotation continues, regardless of the position of the axis of rotation.

A modification of the invention is shown in Figs. 7 and 8. In this embodiment of the invention, the housing 34 is similar to housing 2, is also advantageously made of glass, but instead ofv having therein the cylindrical flange I5, it is pro-'- vided with -a single post 3-5 of glass or insulating material which extends endwise approximately across the chamber 36 of the housing. Afloat member 3l, is similar to member I1 of Figs. 1 to 6, slidingly confined on the post 3-5 so as yto move endwise of the chamber 36 freely and a spring 38 acts between this float member and an end of the chamber 36 so as to yieldingly and resiliently urge the float member into that end zone of the chamber 36 which is farthest from the axis of rotation, it being understood that the housing 34 is mounted on the rotatable block 1 of shaft I0 in the same manner as shownin Figs. 1 to 3 for the housing 2. A body 39 of mercury is disposed in, but only partially fills, the chamber 36, and the chamber 36 also contains an inert atmosphere.

A common conductor 40, and branch conductors 4| and 42, extend from the base end of the housing nearest the axis of rotation A-B into the chamber 36 and across the chamber to different distances into this outermost end zone. The common conductor 40 is advantageously wound spir-ally on the inner periphery of the housing forming the chamber 36, and substantially to the bottom of the body of the mercury confined in the outer end zone of the chamber 36. The conductors 4| and 42 extend to diiTerent distances into the mercury confined in said end zone, and the float member 31 is urged well into the mercury so as to displace the mercury normally into contact with both of the conductors 4I and 42, as shown in Fig. 7. When this embodiment of the switch element is rotated about the axis A-B, the centrifugal forces will confine the mercury in the outer end zone of the housing, and as the speed increases, the centrifugal forces will force the mercury outwardly sufficiently to displace, radially toward the axis of rotation, the float member 31 which allows the mercury to recede first from engagement with the conductor 4| at one speed, then at a higher speed also from the conductor 42. The conductor 4| corresponds in function to the conductor 22 of Fig. 3. This switch may be connected in circuits in the same wayl as explained for the embodiment shown in Figs. 1 to 3, either to contro] signals or other circuits. or the speed of the motor. The branch circuits through the conductors 4| and 42 may be made effective or ineffective by a branch circuit switch which is similar to switch 33.

It is believed that the operation of the device will be understood from the foregoing description. It will be understood that While a common conductor and two branch circuits have been shown. any desired number of branch circuit conductors may extend into the chamber at Idifferent distances into the body of mercury so as to provide for e. greater range of control of circuits as the mercury recedes from the conductors progressively while the speed of rotation increases. Inasmuch as the chambers of both forms of switch element contain an inert atmosphere, any arcing that occurs between the mercury and the conductorsy will have no materially destructive action on the conductors or the mercury. The arc is wholly enclosed within the sealed chamber, so that if used in an atmosphere containing explosive gases, there is no danger of an explosion through ignition of the explosive` gases by the arc. Such a switch m-ay, therefore, advanta geously be used as an explosion proof starter for the starting coils of an alternating current motor, so as to cut out those starting coils after a selected, initial speed of rotation has been reached. Such a switch needs no lubrication in` its interior and it is, therefore, useful with a starting circuit for refrigerator motors of the unit sealed type. Many other uses will be obvious from the foregoing examples.

While I have referred to mercury as the preferred conducting liquid within the switch, because it is an excellent conductor of relatively low resistance, and has a high specific gravity, it will be understood that within the broadest conception of the invention, any other electricity conducting liquid may be used. if desired, in which case, the float member will be of a type of construction or material which will float in that conducting liquid. When using mercury, the conductors within the chambers will be of a metal or alloy which is not affected by mercury. For example, pure iron is very suitable for this purpose because it is unaffected. by mercury, but other alloys which have been designed for use in mercury tubeswitches may also be employed. When any other conducting liquid is employed, the metal of the conductors will be one that is chemically inert to that liquid.

It will be understood that various changes in the details, materials and arrangements of parts, which have been hereinl described and illustrated in order to explain the nature of the invention. may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim:

l. A switch comprising a housing having a closed chamber containing an inert atmosphere. a body of electricity conducting liquid within and only partially filling said chamber. means mounting said housing for rotation bodily about an axis eccentric to said chamber, a member floatable in said liquid and within and only partially filling said chamber, said chamber having a portion guiding said member into and out of the zone of said chamber furthest from said axis, means resiliently urging said member into said zone in a direction away from said axis, and circuit connections connected and disconnected by selected variations in the relative movements of said liquid and member, during rotation of said housing, under the opposing actions of said urging means and of said centrifugal forces tending to displace said member out of said zone with said liquid.

2. A mercury tube switch comprising a housing having a closed chamber containing an inert atmosphere, a. body of mercury without and only partially filling said chamber, means mounting said housing for rotation bodily about an axis eccentric to said chamber, a member oatable in said mercury and within and only partially nlling said chamber, said chamber having a portion guiding said member into and out of the zone of said chamber furthest from said axis, means resiliently urging said member into said zone in a direction away from said axis, and contact means within said chamber and connected and disconnected by said mercury during rotation of said housing about said axis above and below a selected speed as said mercury and member displace each other under the opposing actions of said urging means and of centrifugal forces due to said rotation.

3. A mercury tube switch comprising a housing having a closed Chamber containing an inert atmosphere, means mounting` said housing for rotation about an axis eccentric to said chamber, a means floatable in mercury contained within said chamber and movable therein in a direction toward and irorn said axis and into and out of the zone of said cham er furthest from said axis, a body of mercury within and only partially lling the remainder of said chamber but of suicient quantity to displace said member in said zone towards said axis by centrifugal forces created by rotation of said housing about said axis, means resiliently opposing such displacement of said member by said mercury, and contact means within said chamber and disposed to connect and disconnect an electric circuit through said mercury during rotation of said housing about said axis above and below a selected speed, as the exposed mercury surface moves toward and from said axis by varying displacement of said member by opposing actions of said opposing means and o-f centrifugal forces due to said rotation.

4. A mercury tube switch comprising a housing having a closed chamber containing an inert atmosphere, means mounting said housing for rotation about an axis eccentric to said chamber, a body of mercury within and only partially filling said chamber, a. member in said chamber and movable back and forth therein to displace some of said mercury or to be displaced by the mercury, means yieldngly urging said member into said mercury to displace it in opposition to the movement of the mercury by centrifugal forces created by rotation of said housing, and Contact means within said chamber for opening and cles ing a circuit through said mercury as said mercury and member displace each other under the opposing actions of said urging means and centrifugal forces.

5. A mercury tube switch comprising a hous ing having a closed chamber containing an inert atmosphere, means mounting said housing for rotation about an axis eccentric to said chamber, said housincr having an annular flange projecting from one wall of said chamber, which is that nearest said axis, towards the opposite wall of the chamber and opening to said chamber adjacent said opposite wall, a member oatable in mercury disposed within the space encircled by said flange and slidable in said housing in directions between said walls, a spring in said space and acting between said housing and member to urge said member yieldingly in a direction towards said opposite wall, a body of mercury within and only partially filling said chamber, and contact means within said chamber in position to establish and break a circuit through it and said mercury as said mercury and member displace each other under opposing actions of said spring and centrifugal forces acting on said mercury, as the speed of rotation varies from a selected speed.

6. A mercury tube switch comprising a housing having a closed chamber containing an inert atmosphere, means mounting said housing for rotation about an axis eccentric to said chamber, said housing having two side by side compartments communicating with each other at the end furthest from said axis, a member floatable in mercury disposed within one of said compartments and movable freely therein in a direction toward and from said axis, a spring in said one compartment yieldingly urging said member in a direction away from said axis, a body of mercury within said chamber and suicient in amount, to enter both of said compartments, when confined in said end furthest from said axis, and exert a buoyant action on said member, and contact means within said chamber for opening and closing a circuit through said mercury as said mercury and member displace each other to a predetermined extent under the opposing actions of said spring and centrifugal forces.

'7. A mercury tube switch comprising a housing having a closed chamber containing an inert atmosphere, means mounting said housing for rotation about an axis eccentric to said chamber, a member iloatable in mercury disposed in said chamber and movable therein in a direction towards and from said axis, means resiliently urging said member in a direction away from said axis, a quantity of mercury within said chamber and suilicient to exert a substantial buoyant effort on said member towards said axis when the mercury is confined in the end of said chamber furthest from said axis, and contact means within said chamber and cooperating with said mercury to open and close a circuit therethrough as the mercury and member' displace each other under the opposing actions of said urging means and centrifugal forces acting on said mercury and member as the speed of rotation of the housing varies on opposite sides of a predetermined speed.

8. A mercury tube Switch comprising a housing having a closed chamber containing an inert atmosphere, means mounting said housing for rotation about an axis eccentric to said chamber, a member fioatable in mercury disposed in said chamber for movement therein in a direction toward and from said axis, a spring resiliently urging said member in a direction away from said axis, a body of mercury within and only partially filling said chamber, and a plurality of conductors within said chamber, extending in spaced relation to each other in the direction of movement of said member, toward the end of said chamber furthest from said axis and terminating at different distances from said chamber end such that when said housing is rotated, the centrifugal forces acting on said mercury will confine it in said chamber end and displace said member against said spring until said mercury separates from one of said conductors when a predeter mined speed of rotation is exceeded; whereby a circuit through said mercury and conductors may be broken when said speed of rotation is exceeded.

9. A switch comprising a housing having a closed chamber containing an inert atmosphere, a body of a liquid within and only partially lling said chamber, means mounting said housing for rotation about an axis eccentric to said chamber, a member floatable in said liquid and within and only partially filling said chamber, means for urging said member into said liquid to displace a portion of it in opposition to centrifugal forces urging said liquid in a direction opposing said displacement, and switch means within said chamber and controlled by the relative displacement of said liquid and member.

10. A switch comprising a housing having a sealed chamber containing an inert atmosphere, a body of electricity conducting liquid within and only partially filling said chamber, resilient means within said chamber yieldingly urging said liquid in a direction out of one end of said chamber, but which may be overcome by the liquid when the 11. A switch comprising a housing having a sealed chamber containing an inert atmosphere,

' a body of liquid within and only partially filling liquid is forced into said one end by centrifugal l forces, a conductor extending into said chamber from the outside and within the chamber having an exposed contact area disposed for engagement with said conducting liquid when the latter is displaced from said one end of said chamber by said resilient means, but separating from said liquid when centrifugal forces overcome said resilient means and displace said liquid out of contact with said contact area, and an electrical connection to said liquid.

said chamber, an object smaller than said chamber and of different density than said liquid, disposed in said chamber for movement back and .forth in a direction between the ends of said chamber, means yieldingly urging said object in one direction in said chamber to vary the liquid level in said chamber when the liquid is confined in one end of said chamber by varying displacement of said liquid by said object, whereby when the housing is rotated about an axis at a distance from said one chamber end, and nearer the other end of said chamber, centrifugal forces acting on said object and said liquid will urge them into said one chamber end, and the net result of such forces and yieldingly urging means will cause a variation in the position of the exposed surface of the liquid in the chamber with changes in speed, and conducting parts within said chamber connected and disconnected by the variations in the position of the exposed surface of said liquid in said chamber.

` HARRY L. LAMBERT. 

